Why won't my google web app won't load on my google site in Safari?

I have made a simple Google Site that runs a Google Web App that I wrote and published. The Web App pulls data from a Google Sheet. The Web App runs perfectly if you view my site in Chrome, but doesn't load at all if you view the site in Safari (the rest of the Site content loads fine though). Why would this be? Are Google Web Apps supported in Safari?

In case it matters, below is what my Web App's doGet() outputs. It's not pretty, I know. I'm planning to learn how to use templated HTML outputs. Figuring out how to output HTML code as a string is a stepping stone, so to speak.

var HTMLString = "<font face=arial><table align=center><tr><td>" +
  "<h3 align = center>Album no. " +
  "<font color=#1abc9c>" + albumrand + "</font> picked by <font color=#1abc9c>" + pick + "</font>:" +
  "</h3>" +
  "<h2 align = center><font color=#1abc9c>" + title + "</font>" +
  "</br>by</br>" +
  "<font color=#1abc9c>" + artist + "</font>" +
  "</h2>" +
  "<h4 align=center> Refresh page for another pick</br>| Pull down (mobile) | F5 (desktop) |</h4>" +
  "</td></tr></table></font>";

return HtmlService.createHtmlOutput(HTMLString);